1. Technical Field
The invention relates to suspension systems for vehicles, such as trailers and trucks. More particularly, the invention relates to a suspension assembly having an air spring. Even more particularly, the invention relates to a more compact air spring suspension assembly with the air spring located between frame rails of a vehicle to provide a lower center of gravity than traditional suspension systems.
2. Background Information
Truck or trailer suspension systems should be as safe, durable, and as economical as possible. Often these characteristics conflict and compete, thus necessitating a compromise of one characteristic against another characteristic, which often results in a suspension system being less than ideal. For example, safety considerations dictate that the suspension be sufficiently rigid in its various planes to maintain the vehicle's line of travel. However, safety also necessitates that the suspension be sufficiently flexible or resilient to allow (i.e. take up) deflections caused by articulation forces experienced during operation of the vehicle. Durability includes the ability to resist degeneration (damage) which occurs from the deflections. Durability conflicts with economical cost involved in achieving safety and durability.
One type of suspension, the trailing arm suspension, has a variety of undesirable characteristics. For example, trailing arm suspensions are brake reactive. That is, when a vehicle's brakes are applied, the suspension will tend to compress thereby reducing the suspension's effectiveness. Similarly, when the brakes are applied as the vehicle moves in reverse, the suspension will tend to rise up, and pivot about the single trailing arm pivot, again reducing the suspension's effectiveness. Further, most trailing arm suspensions suffer from dock walk because they move toward or away from the loading dock as the suspension moves up or down with the brakes locked. This movement is caused from air draining off the air springs, or as a result of loads added to or removed from the vehicle, or the temperature changes that occur as the trailer remains parked by the dock. Dock walk occurs primarily because of rotation of the beam, axle and tire assembly when the brakes are locked. As the suspension travels vertically with the brakes locked it rotates the tires causing the tires to move the vehicle horizontally. If the trailer is positioned adjacent a dock, it causes the trailer to move toward or away from the dock as a result of the movement or rotation about the single pivot point. Therefore, a better suspension system is needed.
The same reference numbers in different drawings refer to the same component.